This invention relates to an apparatus for determining the explosion limits of a flammable gas. More particularly, the invention relates to an apparatus which safely withdraws and ignites wet, corrosive, flammable gases from gas streams and determines the lower or upper explosion limit of the gases.
Various devices for determining the explosive characteristics of gases have been previously described. For example, U.S. Pat. No. 263,939 describes an automatic system for continuously testing air, containing methane, in a mine. In this system, air is pulled from the mine by bellows into a chamber where it is ignited by a spark from an induction-coil or an incandescent platinum wire. The resulting pressure increase is sensed by a manometer. A similiar system is described in U.S. Pat. No. 977,947 with the exception that the explosion is indicated by an audible and visible signal. In U.S. Pat. No. 3,026,711, a certain quantity of a flammable gas is compressed and the heat of combustion measured by such means as a thermocouple. If desired, a measuring tube made of transparent material can be affixed to the compression chamber. The apparatus described in U.S. Pat. No. 3,768,313 is used to determine the least amount of energy to ignite a gas by the spark gap ignition method.
Other devices to measure characteristics of flammable gases have also been described in the prior art. Thus, U.S. Pat. No. 3,027,751 describes means for observing the velocity of a blast wave by measuring the change in resistance of a wire at the locus of a moving flame front, while the detector described in U.S. Pat. No. 3,315,081 employs photocells to measure the burn time of a sample ignited by a spark. In U.S. Pat. No. 3,434,336, an explosion barrier is described in which hot wires, sparks from impact, spontaneous combustion, static, etc. are used to ignite a gas in a two-chamber explosion test apparatus. The device described in U.S. Pat. No. 3,978,877 employs spark plug ignition from a conventional capacative discharge ignition unit to detect flammable gas mixtures.
While suitable for specific applications, none of the prior art devices are adequate for detecting the explosion limits of corrosive gases, and particularly wet, corrosive gases. Accordingly, there is a need for a device which will allow for the sampling and testing of corrosive gases from process streams, waste streams, etc., in a reproducible manner without damaging the test apparatus.